(Not Applicable.)
(Not Applicable.)
The present invention relates to throttles for internal combustion engines, and in particular, to an improved return spring assembly for use with electronic throttles.
Electronic or xe2x80x9cdrive-by-wirexe2x80x9d throttle systems for use in automobiles and other powered by internal combustion engines are well known in the art. In such systems, the acceleration pedal is not mechanically connected to the throttle valve (which controls air volume flowing through the throttle body to the combustion chamber). Instead, acceleration input is electrically coupled to a potentiometer which detects analog input values sent to an electric motor. The electric motor is coupled via a shaft and gear assembly to the throttle valve. The motor actuates the throttle valve to open according to the acceleration input. The acceleration input is typically sampled and averaged periodically to prevent rapid acceleration and deceleration of the engine. A return spring, such as a compression or torsion spring, is connected to the valve shaft to bias the throttle valve closed. When no acceleration input is received, for example, when the ignition is turned off, the throttle valve is closed by the motor and biased closed by the return spring. In the event of loss of motor power, the return spring cooperates with an auxiliary spring to return the throttle valve to an intermediate position, allowing the vehicle to be driven at a low, constant speed. One such electronic throttling system is disclosed in U.S. Pat. No. 4,867,122.
In typical electronic throttling systems, the throttle valve drive assembly is assembled to a throttle body and enclosed by a housing cover. The return spring must be assembled and wound (or tensioned) as needed to bias the throttle valve closed. The return spring must be wound sufficiently to overcome frictional forces in the gear and motor assembly when closing the throttle valve. As it is tensioned, the return spring tends to move and/or uncoil unless secured in place. Consequently, there must be a catch to which the free end of the return spring can be attached once it is wound. Since, the housing cover is not yet assembled this catch is typically a separate component requiring additional assembly, rather than being an integral part of the housing cover. Moreover, since the spring is wound before the housing cover is assembled, the spring can uncoil if not properly held by the catch or if bumped when assembling the housing cover, thereby requiring the spring to be reset. Thus, assembling typical throttle return springs can be difficult and time consuming.
Accordingly, a need exists for an improved throttle return spring assembly that can be easily assembled.
The present invention provides an electronic throttle return spring assembly that can be completely assembled before the return spring is tensioned. Specifically, the throttle return spring assembly includes a shaft extending along a rotation axis and connected to a valve. The shaft is rotated to adjust the valve as needed to close and open a throat of a throttle. A return spring is positioned concentric with the rotation axis and has a first leg connected to the shaft and a second leg extending axially. A guide, generally concentric with the rotation axis, allows rotation of the return spring about the rotation axis and restricts lateral translation of the return spring. The guide has an arcuate inner radial wall that defines a catch projecting radially inward. Rotating the second leg so as to follow the arcuate wall and engage the catch tensions the return spring.
In one aspect of the invention, the arcuate wall defines a catch groove in which the second leg is disposed. The arcuate wall also defines a relief slot of sufficient radius from the rotation axis such that the second leg can be disposed therein before being tensioned.
In another aspect of the invention, the guide is formed as an integral part of a cover to a gear housing adjacent to the throttle. Preferably, the guide is a rigid structure insert molded in the cover.
In another aspect, a cap covers the guide and the return spring. The cap has fingers that engage with the guide to secure the cap in place. The cap also has a stop member projecting axially and positioned to prevent the second leg from exiting the catch groove and releasing the return spring. The stop member is positioned a distance from an opening of the catch groove less than the diameter of the second leg.
In yet another aspect of the invention, a winding tool may be used to wind the return spring used the throttle body has been assembled. The winding tool includes a handle at one end opposite a body having a central bore and a radial recess. In use, the bore of the winding tool is fit over one end of the shaft so that the radial recess receives the second leg of the return spring. The winding tool can pilot about the shaft in a counter-clockwise direction to move the second leg along the arcuate wall to engage the catch.
In a preferred form, an electronic throttle unit has a throttle chamber with a throat in which is disposed a valve rotatable to close and open the throat and a motor and gear assembly contained in a housing attached to the throttle chamber. The motor and gear assembly drives a shaft connected at one end to the valve and at an opposite end to a return spring having a plurality of windings terminating in an axially extending leg. The guide includes a rigid plate integral with a cover to the housing having an opening through which the return spring leg is disposed. The opening is defined by an inner arcuate surface spiraling radially inward to a catch slot. The guide restricts lateral translation of the return spring. The spring leg can be made to follow the arcuate surface thereby tensioning the return spring to bias the valve closed. Disposing the spring leg in the catch slot maintains the return spring under tension.
Thus, the return spring assembly of the present invention allows the return spring and the throttle body to be assembled before the return spring is wound. The integral guide retains the spring and provides a quick and easy means for winding the return spring to the proper tension. A dust cap covers the return spring to keep out debris and has a stop member which prevents the return spring from disengaging the catch.
These and still other advantages of the present invention will be apparent from the description of the preferred embodiments which follow.